1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device of which a size and a weight are reduced and an assembly facility is improved and a method for assembling the liquid crystal display device.
2. Description of the Related Art
In these days, information processing devices have been rapidly developed in a trend with various architectures, functions and faster information processing speeds. Information processed in these information processing devices has an electrical signal format. In order to visually confirm information processed in the information processing device, a display for a role as an interface should be provided.
Recently, a liquid crystal display device which is lighter, and smaller than a CRT type display device has been developed. The liquid crystal display device has functions such as full color and high resolution. As a result, the liquid crystal display device is widely used as a monitor for a computer, a television, or another display device.
The liquid crystal display device applies a voltage to a predetermined molecular arrangement of a liquid crystal to convert the molecular arrangement to another molecular arrangement. The liquid crystal display device converts the changes of optical properties to visional changes and uses the modulation of a light by using a liquid crystal cell.
Liquid crystal display devices are divided into a TN (Twisted Nematic) type and a STN (Super-Twisted Nematic) type, and are also divided into an active matrix display type which uses a switching device and a TN liquid crystal and a passive matrix display type which uses a STN liquid crystal according to the driving type.
The active matrix display type is used in a TFT-LCD and drives an LCD by using a TFT as a switch. The passive matrix display type does not use any transistor and does not need a complex circuit.
Further, liquid crystal display devices may be a transparent liquid crystal display device which uses a backlight or a reflective liquid crystal display device which uses an exterior light source according to a method for using a light source.
The transparent liquid crystal display device which uses the back light as a light source has a heavy weight and a large volume by the existence of the back light, but is widely used since it independently displays an image without using an exterior light source.
FIG. 1 is an exploded perspective view schematically showing a conventional liquid crystal display device. FIG. 2 is a sectional view showing the constructions of the liquid crystal display device shown in FIG. 1.
Referring to FIG. 1, the liquid crystal display device has a liquid crystal display module 130 for displaying images when image signals are applied thereto and front and rear cases 110 and 120 for receiving the liquid crystal display module. The liquid crystal display module 130 includes a display unit 170 having a liquid crystal display panel for showing the images and a backlight assembly 150 for supplying a light to the display unit 170.
The display unit 170 includes a liquid crystal display panel 171, a data side printed circuit board 176, a gate side printed circuit board 175, a data side tape carrier package 178 and a gate side tape carrier package 174.
The liquid crystal display panel 171 has a thin film transistor board 172, a color filter board 173 and a liquid crystal (not shown).
The thin film transistor board 172 is a transparent glass board on which the thin film transistors are formed in a matrix shape. Data lines are respectively connected with source terminals of the thin film transistors and gate lines connected with gate terminals of the thin film transistors. Furthermore, pixel electrodes are respectively formed at drain terminals of the thin film transistors, which are comprised of a transparent conductive material such as Indium Tin Oxide (ITO).
The color filter board 173 is provided to face to the thin film transistor board 172. RGB pixels are formed on the color filter board 173 by means of a thin film process, which gives a predetermined color while the light passes through the color filter board 173. Common electrodes made of the ITO are coated on the front surface of the color filter board 173.
When the thin film transistors of the thin film transistor board 172 are turned on by applying a power source to the gate terminals and the source terminals of the thin film transistors, an electric field is formed between the pixel electrodes of the thin film transistor board 172 and the common electrodes of the color filter board 173. The electric field forces the liquid crystal, which is injected between the thin film transistor board 172 and the color filter board 173, to change the array angle thereof, resulting in the transmissivity of the light being changed. As a result, the desired pixels are obtained.
Meanwhile, a driving signal and a timing signal are applied to the gate lines and data lines of the thin film transistor in order to control the array angle of the liquid crystal and the time of arraying the liquid crystal in the liquid crystal display panel 171. As shown in FIG. 1, the data side tape carrier package 178 that is one of the flexible circuit boards, is attached to the source portion of the liquid crystal display panel 171 to decide a time of applying a data driving signal. On the other hand, the gate side tape carrier package 174 is attached to the gate portion of the liquid crystal display panel 171 to decide a time of applying a gate driving signal.
The data side printed circuit board 176 and the gate side printed circuit board 175, which respectively apply the driving signal to the gate line and the data line as soon as each receives image signals input from the outside of the liquid crystal display panel 171, make contact with the data side tape carrier package 178 for the data line and the gate side tape carrier package 174 for the gate line in the liquid crystal display panel 171, respectively. A source portion is formed on the data side printed circuit board 176 in order to receive the image signals from an information process device (not shown) such as a computer, etc. and then to provide the gate driving signal for the gate line of the liquid crystal display panel 610. A gate portion is then formed on the gate side printed circuit board 175 to provide the gate driving signal to the gate lines of the liquid crystal display panel 171. That is, the data side printed circuit board 176 and the gate side printed circuit board 175 generate and apply the gate driving signal and the data signal for driving the liquid crystal display device and a plurality of timing signals for applying the gate driving signal and the data signal to the gate lines and the data lines of the liquid crystal display panel 171, so as to provide the gate driving signal through the gate side tape carrier package 174 to the gate lines of the liquid crystal display panel 171 and to supply the data signal through the data side tape carrier package 178 to the data lines of the liquid crystal display panel 171.
The backlight assembly 150 is provided under the display unit 170 to uniformly supply the light to the display unit 170. The backlight assembly 150 includes lamp units 161 and 162, which are disposed at both ends of a liquid crystal display module 130, for generating the light, a light guide plate 152 for guiding the light emitted by the lamp units 161 and 162 toward the display unit 170 with changing a pathway of the light, a plurality of optical sheets 153 for making a brightness of the light which is transmitted from the light guide plate 152 uniformly and a light reflecting plate 154, which is provided under the light guide plate 152, for reflecting a leaked light to the light guide plate 152 so as to improve the efficiency of the light.
The display unit 171 and the backlight assembly 150 are received in a mold frame 132 used as a receiving container, in order. The mold frame 132 is provided with a top chassis 140, which is faced and combined to the mold frame 132, for preventing the display unit 171 from departing from the mold frame 132.
Meanwhile, the liquid crystal display device further includes a power supply printed circuit board 135, which has an inverter circuit, for supplying the power source to the lamps of the lamp units 161 and 162 and a signal conversion printed circuit board 134 for converting and providing outer data signals to the printed circuit board 176 for data.
The power supply printed circuit board 135 and the signal conversion printed circuit board 134 are fixed to a rear surface of the bottom chassis 131 by means of a bracket 133, as shown in FIGS. 1 and 2. Particularly, when the top chassis 140 is assembled with the mold frame 132 to make the liquid crystal display module 130, the liquid crystal display module 130 is received in the front case 110. The power supply printed circuit board 135 and the signal conversion printed circuit board 134 are combined to the rear surface of the bracket 133 by means of the screws 134c, 134d and 135b so that supports 134a, 134b and 135a are disposed between the rear surface of the bracket 133 and the power supply printed circuit board 135 and the signal conversion printed circuit board 134. The bracket 133 is combined with the front case 110 by means of screws 133a and 133b. 
Then, a shield case 136 is disposed at the rear surface of the bracket 133 to enclose the power supply printed circuit board 135 and the signal conversion printed circuit board 134. The shield case 136 insulates an electromagnetic wave generated from the liquid crystal display module 130 including the power supply printed circuit board 135 and the signal conversion printed circuit board 134.
As described above, when the bracket 133 and the shield case 136 are combined to the rear surface of the liquid crystal display module 130, the rear case 120 is coupled with the front case 110 to complete the liquid crystal monitor device.
As shown in FIG. 2, the power supply printed circuit board 135 and the signal conversion printed circuit board 134 are mounted on the rear surface of the liquid crystal display module 130 by the combination with the bracket 133 having a predetermined height. Further, the shield case 136 is coupled to the rear surface of the bracket 133 by means of the screws 136a and 136b. 
In the liquid crystal display device, there are many problems as follows.
Firstly, the thickness of the liquid crystal display device increases to the extent of the heights of the bracket 133 and the shield case 136 and the heights of the supports 134a, 134b and 135a for fixing the power-supplying printed circuit board 135 and the signal-converting printed circuit board 134 to the bracket 133.
Secondly, since the bracket 133 made of metal material and the screws are used for mounting the power supply printed circuit board 135 and the signal conversion 134 on the liquid crystal display module 130, the liquid crystal display device can be too heavy.
Thirdly, the power supply printed circuit board 135, the signal conversion printed circuit board 134, the bracket 133 and the shield case 136 are respectively integrated with the liquid crystal display module 130 by means of the screws. Accordingly, the assembling processes of the liquid crystal display device can be complicated.
Fourthly, as a plurality of parts is required for integrating the power supply printed circuit board 135, the signal conversion printed circuit board 134, the bracket 133 and shield case 136 with the liquid crystal display module 130, a cost of manufacturing the liquid crystal display device can be increased.
Fifthly, since the power supply printed circuit board 135 and the signal conversion printed circuit board 134 are placed at a position far away from the lamp units 161 and 162 and the data side printed circuit board 176, as not shown in detail in drawings, there is a problem in that a line for supplying the power source and a line for transferring the signals are longer. Furthermore, when the line for supplying the power source and the line for transferring the signals are longer, it is difficult to stably contain and fix the lines to the liquid crystal display module 130.